Year: 2007
Type: article
Abstract: The fossil record provides structural fingerprints of development from which we can infer the sequence of ontogenetic changes that resulted in the evolution of stems, leaves and roots from the axes of the most ancient vascular plants.From the morphological evidence provided by the fossil record, we can infer developmental changes and test these hypotheses by comparative development in features of extant plants.Reciprocally, as we know more about angiosperm development we can hypothesise the pathways that changed to result in ontogenetic alterations and test these hypotheses by inferences from the morphology of extinct plants evidenced in the fossil records.Examination of the most ancient seed plants has revealed that the evolution of leaves involved a step-wise acquisition of characters.While early seed plant leaves were determinate organs, they did not display complete ab-adaxial identity.The evolution of this feature suggests that ab-adaxial identity evolved from imposition of shoot patterning on the leaf.Comparison of the most ancient seed plants to the most ancient ferns reveals that leaves in each clade evolved through a different sequence of character acquisitions.KNOX proteins are important regulators of meristematic activity and leaf morphology in some angiosperm species.However, KNOX protein expression does not appear to regulate leaf morphology in Ceratopteris.Leaf morphology in Ceratopteris is laid down by marginal meristematic activity.Auxin transport appears to be an important regulator of this marginal meristem.Likewise, auxin transport mechanisms in the isoetalean lycopsids probably evolved in parallel with seed plants to regulate similar aspects of bipolar growth and body plan organization.
Author: Heather Sanders
Institution: Ohio University
Language: English
Subfield: Plant Science
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2600235887